4 Answers
4

For practice you can use the Nikon Wireless CLS. The D700 buildin flash can act as commander, and the SB-900 as TTL slave.
Pro: you can use full TTL capabilities.
Con: range is limited, especially in bright areas. Range can be extended by buying a TTL-Flash-Controller (SB-12?).

Cable is a great start, too: it works very reliable, you can use full TTL, but of course range is limited to cable length.

Pro Wireless triggers (Radiopopper PX, Pocketwizard TTL) will give you full TTL with great reliability and good range, but for a hefty price.

I'd buy a cheap set of radio triggers like the YongNuo RF-602 for learning strobist, and see if this works for you. Of course you need to learn lighting manually for this, but I think this is a good skill to have, even if you are using TTL.

For resources of course have a look at strobist 101 and 102 at www.strobist.com.

That'll help you out with setting up, or at least knowing what they are, light modifiers that you can roll on your own. However, the Strobist site is about the best when it comes to all of this and I can't stress the value in reading through the lesson posted.

Now to answer your question... Pocket Wizards are great, but have a price tag you need to consider and there are other options that, while less reliable, are substantially cheaper while still being pretty good. Again, the Strobist site discusses them, so worth looking. Either way, the PC sync cable should be your last option...

Fro my d300, I can set the main camera to be 'commander' and my sb900 to be 'slave', and make sure that the appropriate channels are used (ie, that the flash is firing on a2, and the slave is listening on a2). Your d700 manual should contain instructions for how to set these things up. The flash will have to 'see' the pulses sent by the camera, ie, be roughly in front of the camera.

Make sure you remember to turn the commander setting off once you're done. At a wedding I shot recently, someone had set their flash to slave mode, and every time I took a shot, their flash fired. Took me a bit to figure out why my shots were so mangled.

As mmr and Sam point out, your D700 can work as wireless master for SB-900. Therefore, everything you need is to set the triggers according to your instruction manual, stick the flash somewhere to the side and try it.

Later you might want to use some light modifiers, and perhaps look into other triggering methods, but as you can use CLS out of the box, there's really no reason not to use it right now. All you need to create photos like this one is a piece of cardboard and a sticky tape.